This invention relates to an alternating current generator for vehicle having a rotor of claw pole type.
FIGS. 13 to 17 show a configuration of a conventional alternating current generator for vehicle. FIG. 13 is a sectional view of the generator, and FIG. 14 is a perspective view of a rotor, and FIG. 15 is a perspective view of a stator, and FIG. 16 is a perspective view of a stator core, and FIG. 17 is a plane view showing a shape of magnetic poles of the rotor. In the drawings, numeral 1 is a front bracket, and numeral 2 is a rear bracket, and numeral 3 is a stator sandwiched between the front bracket 1 and the rear bracket 2. The stator 3 comprises a stator core 4 and a three-phase stator coil 5 inserted into a slot 4a of the stator core 4 as shown in FIGS. 13, 15 and 16.
In FIGS. 13 and 14, numeral 6 is a rotor of claw pole type. The rotor 6 comprises a rotating shaft 7 whose both ends are supported by the front bracket 1 and the rear bracket 2, a first rotor core 8 and a second rotor core 9 mounted on this rotating shaft 7, a field coil 10 wound between both of the rotor cores 8 and 9, fans 11 and 12 provided in the back of both of the rotor cores 8 and 9, a pulley 13 provided outside the front bracket 1 side of the rotating shaft 7, and a slip ring 14 provided inside the rear bracket 2 side of the rotating shaft 7 for supplying a current to the field coil 10. Numeral 15 is a brush for supplying a current to the slip ring 14, and numeral 16 is a brush holder for holding this brush 15, and numeral 17 is a commutator for commutating alternating current output of the stator coil 5, and numeral 18 is a regulator for regulating a current of the field coil 10 to control an output voltage of the stator coil 5.
Numerals 19 and 20 are magnetic poles axially extending to the inner diameter of the stator core 4 from the first rotor core 8 and the second rotor core 9 through a predetermined air gap. A plurality of the magnetic poles 19 extending from the first rotor core 8 and the magnetic poles 20 extending from the second rotor core 9 are respectively provided according to the number of poles of the generator and are arranged so as to have engagement alternately through predetermined gaps 21 and 22 between the magnetic poles and are magnetized in north poles and south poles alternately by excitation of the field coil 10. Also, the magnetic poles 19 and 20 are formed into an isosceles trapezoid whose width is narrowed in the rotational direction toward the top end as shown in FIG. 17, and both the end surfaces of the rotational direction are formed in a straight line at a predetermined angle of inclination and thus, a line pitch between centerlines indicated by broken lines of the gaps 21 and 22 between the magnetic poles also changes in a straight line as shown in FIG. 17.
In order to improve efficiency of the generator generally, the centerlines indicated by the broken lines of the gaps 21 and 22 between the magnetic poles are set so as to incline in the range from about 60xc2x0 to about 120xc2x0 where an electrical angle between the adjacent magnetic poles 19 and 20 is set to 180xc2x0 and, for example, the center of the magnetic pole 19 is set to 0xc2x0 as shown in FIG. 17. Also, chamfered parts 19a and 20a for smoothing a magnetic flux density of the air gap formed between the magnetic poles 19, 20 and the stator core 4 and suppressing electromagnetic noise are formed in the corner of the outer surface opposite to the stator core 4 of the magnetic poles 19 and 20 and both the end surfaces of the rotational direction.
In the conventional alternating current generator for vehicle formed in this manner, when current is passed through the field coil 10 from a battery (not shown) mounted in the vehicle via the brush 15 and the slip ring 14, the magnetic poles 19 and 20 are excited alternately in the north pole and the south pole and the rotor 6 is driven by an internal combustion engine through the pulley 13 and thereby, the magnetic poles 19 and 20 give a rotating magnetic field to the stator core 4 and a three-phase alternating current voltage is generated in the stator coil 5 and this alternating current voltage is commutated by the commutator 17 for direct current and electric power is supplied to a load (not shown). Then, the regulator 18 holds an output voltage of the stator coil 5 to a constant value by controlling the passed current of the field coil 10.
In the alternating current generator for vehicle as described above, the rotating magnetic field given to the stator core 4 by the magnetic poles 19 and 20 is not a complete sine wave but a waveform including higher harmonics, and also an output current given to the load by power generation of the stator coil 5 is a current including higher harmonics. In operation of the generator, electromagnetic attraction force occurs between the magnetic poles 19, 20 and the stator core 4 due to interaction between the rotating magnetic field including higher harmonics and a magnetic field caused by an output current including higher harmonics, and this electromagnetic attraction force acts as applied vibration force, with the result that the stator core 4 and the magnetic poles 19, 20 vibrate to cause electromagnetic noise. Especially, a particular higher harmonic component among this electromagnetic noise interferes with quietness in the vehicle as abnormal sound, and various measures of noise have been taken.
For example, a technique disclosed in JP-A-54-134309 is also one of the measures of noise, and this technique notes that change in torque caused by periodic passage of the magnetic poles 19 and 20 arranged at regular pitches through the side of an inner diameter of teeth 4b arranged at regular pitches of the stator core 4 shown in FIG. 16 acts as applied vibration force to the stator core 4, and noise intends to be reduced by setting arrangement of the magnetic poles 19 and 20 at irregular pitches. According to this technique, the noise resulting from vibration the stator core 4 due to the change in torque is reduced, but the noise resulting from the electromagnetic attraction force between the stator core 4 and the magnetic poles 19, 20 cannot be reduced. Also, in this technique, for example, since the gaps 21 and 22 between the magnetic poles provided between the magnetic poles 19 and 20 shown in FIG. 14 are set at irregular pitches, the narrow gaps between the magnetic poles occur, so that there were side effects that a leakage magnetic flux between the magnetic poles 19 and 20 increases and output of the generator decreases.
The invention is implemented to solve such problems, and it is an object of the invention to obtain an alternating current generator for vehicle capable of effectively suppressing occurrence of abnormal sound without decrease in performance by reducing applied vibration force of higher harmonic components which can possibly become noise.
An alternating current generator for vehicle according to the invention comprises a stator core in which a three-phase stator coil is wound and inserted into slots, a first rotor core and a second rotor core which are provided in the side of an inner diameter of this stator core and rotate with a rotating shaft, a field coil for magnetizing these first and second rotor cores in different magnetic poles, and a plurality of magnetic poles which are provided so as to extend to an axial direction of the rotating shaft from the first and second rotor cores and are arranged so as to have engagement alternately through predetermined gaps between the magnetic poles and also are opposite to the surface of the inner diameter of the stator core through an air gap, and by forming these magnetic poles in a stepwise shape having a plurality of parts in the axial direction and setting the respective parts to different widths in a rotational direction, a pitch of the rotational direction between centerlines of the gaps between the adjacent magnetic poles is configured so as to change stepwise in the axial direction.
Also, the pitch of the rotational direction between the centerlines of the gaps between the adjacent magnetic poles is set to the range from 200xc2x0 to 220xc2x0 in a first part and the range from 140xc2x0 to 160xc2x0 in a second part using an electrical angle. Further, the pitch of the rotational direction between the centerlines of the gaps between the adjacent magnetic poles is set to the range from 220xc2x0 to 230xc2x0 in a first part, the range from 190xc2x0 to 200xc2x0 in a second part, the range from 160xc2x0 to 170xc2x0 in a third part and the range from 130xc2x0 to 140xc2x0 in a fourth part using an electrical angle.
Also, an alternating current generator for vehicle comprises a stator core in which a three-phase stator coil is wound and inserted into slots, a first rotor core and a second rotor core which are provided in the side of an inner diameter of this stator core and rotate with a rotating shaft, a field coil for magnetizing these first and second rotor cores in different magnetic poles, and a plurality of magnetic poles which are provided so as to extend to an axial direction of the rotating shaft from the first and second rotor cores and are arranged so as to have engagement alternately through predetermined gaps between the magnetic poles and also are opposite to the surface of the inner diameter of the stator core through an air gap, and these magnetic poles are formed in a substantially trapezoid shape of taper to the axial direction and also a part with a large angle of inclination to the axial direction is provided in the center of the axial direction and the axial length of this part is set to 30% or shorter to the whole axial length of the magnetic poles.
Further, corners formed by the surface opposite to the inner diameter of the stator core of the magnetic poles and both sides of the rotational direction are chamfered. Furthermore, the number of slots per phase every pole provided in the stator core is one. Also, the number of slots per phase every pole provided in the stator core is two.